The present application relates to medical monitoring and clinical data devices for monitoring the physiological condition of a patient. It finds particular application in the use of a prioritized schedule for spectrum reallocation.
The rapid growth in physiological sensors, low power integrated circuits and wireless communication has enabled a new generation of medical body area networks (MBAN) to be used to monitor patients. MBANs provide low-cost wireless patient monitoring (PM) without the inconvenience and safety hazards posed by wired connections, which can trip medical personnel or can become detached so as to lose medical data. In the MBAN approach, multiple low cost sensors are attached at different locations on or around a patient, and these sensors take readings of patient physiological information such as patient temperature, pulse, blood glucose level, electrocardiographic (ECG) data, or so forth. The sensors are coordinated by at least one proximate hub or gateway device to form the MBAN. The hub or gateway device communicates with the sensors using embedded short-range wireless communication radios for example conforming with an IEEE 802.15.4 (Zigbee) short-range wireless communication protocol. Information collected by the sensors is transmitted to the hub or gateway device through the short-range wireless communication of the MBAN, thus eliminating the need for cables. The hub or gateway device communicates the collected patient data to a central patient monitoring (PM) station via a wired or wireless longer-range link for centralized processing, display and storage. The longer-range network may, for example, include wired Ethernet and/or a wireless protocol such as Wi-Fi or some proprietary wireless network protocol. The PM station may, for example, include an electronic patient record database, display devices located at a nurse's station or elsewhere in the medical facility, or so forth.
MBAN monitoring acquires patient physiological parameters. Depending upon the type of parameter and the state of the patient, the acquired data may range from important (for example, in the case of monitoring of a healthy patient undergoing a fitness regimen) to life critical (for example, in the case of a critically ill patient in an intensive care unit). Because of this there is a strict reliability requirement on the MBAN wireless links due to the medical content of the data. However, the current spectrum allocations and regulations for medical wireless connectivity do not meet the strict requirements of MBAN, including medical-grade link robustness, ultra low-power consumption and low-cost, due to either limited bandwidth or uncontrolled interference.
Short-range wireless communication networks, such as MBAN systems, tend to be susceptible to interference. The spatially distributed nature and typically ad hoc formation of short-range networks can lead to substantial spatial overlap of different short range networks. The number of short-range communication channels allocated for short range communication systems is also typically restricted by government regulation, network type, or other factors. The combination of overlapping short-range networks and limited spectral space (or number of channels) can result in collisions between transmissions of different short range networks. These networks can also be susceptible to radio frequency interference from other sources, including sources that are not similar to short-range network systems.
Frequency spectrum regulation policies try to increase the spectrum use efficiency. One way to increase efficiency is to allocate an opportunistic spectrum specifically for MBAN applications and services as secondary users of a spectrum that has been previously allocated to other services on a primary basis. The basic idea of an opportunistic spectrum is to allow secondary users to opportunistically utilize the spectrum that has been previously allocated to primary users as long as such secondary users do not introduce harmful interference to the primary users. For example, it has been proposed in the U.S. to open the 2360-2400 MHz band (MBAN spectrum), currently assigned to others, to MBAN services as a secondary user. Similar proposals have been made or are expected to be made in other countries. The wide bandwidth, interference-free and good propagation properties of the MBAN spectrum would meet the strict requirements for medical-grade connectivity. In order to achieve co-existence between primary users and secondary users, some restrictions (or spectrum regulation rulings) would be put on the spectrum use of secondary users.
For example, when the allocated MBAN spectrum is used on a secondary basis, the secondary user would have to protect the primary user in that spectrum. For example, to protect the primary users, secondary users are often required to provide appropriate mechanisms to vacate the spectrum of the primary user when the primary user wants to use the spectrum. To accomplish this, enforcement mechanisms are needed. The present application proposes to integrate a mechanism in the MBAN systems to guarantee compliance with the MBAN regulations.
The simplest spectrum reallocation mechanism includes sending and receiving reallocation requests through a network connection. For example, once a MBAN coordinator receives a spectrum request from the primary user, the MBAN coordinator sends a spectrum reallocation request to backhaul access points (APs) through the hospital network connection. In response to receiving the reallocation requests from the MBAN coordinator, the backhaul AP broadcasts the request to all the MBAN hub devices that are connected to the backhaul AP via backhaul links. The MBAN hub device then disables the channels within the MBAN spectrum requested by the primary user. If the MBAN hub device is operating within the reallocated MBAN channel, the MBAN hub device initiates a dynamic channel selection to pick a new channel other than the reallocated spectrum. Once a MBAN hub device selects a new MBAN channel, it transmits a channel switch command to its corresponding MBAN devices within its MBAN network to move the MBAN network to the new channel. Once all the MBAN networks finish their channel switch operations, the MBAN spectrum requested by the primary user is vacated and ready for the primary use.
However, this solution has performance issues due to the acuity level and quality of service requirements and the potential number of MBAN networks within a healthcare facility. For example, a situation may occur where two MBAN networks exist, MBAN A operating on Channel 1 and MBAN B operating on Channel 2. MBAN A bears a high-acuity service and MBAN B bears a low-acuity service. In the example, Channels 1 and 2 are within the reallocated MBAN spectrum and Channels 3 and 4 are both idle and outside the reallocated MBAN spectrum and Channel 3 has better quality (i.e. less in-band noise-plus-interference floor) than Channel 4. If the primary user requests reallocation of the MBAN spectrum of Channels 1 and 2, the MBAN coordinator transmits spectrum reallocations requests from the backhaul AP to the MBAN hub devices of MBAN A and B (referred to as Hub A and Hub B respectively). In response to receiving the reallocation request, Hub A and Hub B performs channel scanning and dynamic channel selection operations independently (i.e. in a distributive way). A possibility exists that both Hub A and Hub B detects that Channel 3 is idle and select it. Therefore, MBAN A and MBAN B co-locate on Channel 3 and their transmissions could collide with each other even though there are two idle channels (Channel 3 and 4) available. The collisions degrade the performance of both MBAN A and MBAN B. In another case, MBAN B may initiate dynamic channel selection earlier than MBAN A and choose Channel 3 as its new channel due to the channel's better quality. If MBAN A initiates dynamic channel selection, Channel 4 is the only available channel and MBAN A will be left to operate on Channel 4, which has a worse quality compared to Channel 3, even though it has a higher acuity level than MBAN B. This may degrade the quality of service of performance of MBAN A.
The present application provides a new and improved system and method for spectrum reallocation which overcomes the above-referenced problems and others.